Existing methods and systems for operating a geofence for tracked assets typically use an algorithm that base a definition of a geofence boundary on a predetermined geographical location.
A typical tracking device existing in the art uses a global positioning satellite (“GPS”) to determine the current location of the device. A wireless transceiver coupled to the GPS receiver, and GPS processor, transmits information from the GPS processor toward a central computer for processing. The algorithm then compares the current location coordinate of the GPS receiver to predetermined coordinates, or other definition of a geometric shape, such as an equation of a circle centered at a given location predetermined by a user at the central computer, to determine whether the GPS device, and thus what it is fixed to, is bounded by the geometric shape. If not, the central computer may generate a notification that the geometric shape does not bound the GPS device.
While such an approach performs the desired function of generating the notice when a tracked asset leaves the predetermined geographical boundary, for example, the approach also has drawbacks. The drawbacks include excessive power usage and wireless transmission bandwidth usage. To perform a comparison of the current location to the geographical boundary, a system may periodically transmits current location coordinates to the central server, and then the central server performs the comparison and generation of alerts if the comparison indicates that the geographical boundary does not bound the tracked asset. Since each transmission of a data unit, such as a packet, cost money, each periodic transmission of a data unit incurs a cost in air time.
In addition, a person, or organization, that it tracking a particular asset may want to track an asset to determine that it has not moved outside a boundary when the asset is supposed to be turned off. For example, if someone leaves a car parked at an airport, he may want to log on to a web site and determine that his car has not moved from the airport—movement from the airport would indicate a stolen vehicle situation although the user might have permitted service personnel to move the car while at the airport for servicing or maintenance. In such a scenario, upon each periodic transmission of data the wireless transceiver would drain the vehicle's battery by a measurable amount.
Furthermore, in another scenario, a service provider providing roadside assistance in response to an emergency call, distress call, or call for assistance, may have an interest in tracking an asset that it does not own. If a provider dispatches a field unit (i.e., a mechanic in a repair truck, or a tow truck) to provide assistance to a requesting motorist the motorist may either repair the car himself before the field unit arrives, or another responder may arrive first and render aid. In such a situation, the first service provider may end up allocating its resource to the motorist, only to discover upon arrival at the location where the motorist initiated the request for assistance that the motorist has left.